In this study, hydrodynamics and physiology of microorganisms were investigated in a new type membrane
bioreactor, MHCR, which is a membrane coupled HCR (High performance Compact Reactor) having very high
COD removal efficiency. The degree of interference caused by inserting a submerged membrane was evaluated
quantitatively by measuring the air suction rate and overall oxygen transfer coefficient (kL, a). Despite such
interference, MHCR showed greater oxygen transfer efficiency than HCR under particular hydrodynamic conditions.
Higher recirculation rate generally resulted in a higher turbulence and thus alleviated membrane fouling.
When the recirculation rate was too high however, the microbial flocs were broken by fluid shear and membrane
permeability was decreased rapidly. All these results were elucidated through not only physicochemical
but also microbiological factors.